This invention relates to a solar tracking mechanism for continuously tracking the movement of the sun with time to effectively obtain radiant energy from the sun.
Recently, it has been required to develop a solar tracking technology of concentrating type for effectively obtaining radiant energy from the sun. For these purposes, for example, various tracking systems each utilizing a driving motor and electronic control devices therefor were developed or proposed. However, these tracking systems require a continuous electric power supply and are somewhat complicated for technology transfer to developing countries where sunshine is so abundant that the utilization of solar energy is favorable while, however, electric power supply networks have not yet been adequately developed. Taking the above facts into consideration, some tracking mechanisms for solar collectors were proposed in, for example, U.S. Pat. Nos. 3,982,526, 4,044,752, and 4,356,616, which require no electric power supply and no electronic control devices for simplifying their mechanisms.
Each of the former two U.S. Patents discloses a device which is provided for turning a solar collector about either a polar axis or an east-west horizontal axis. The devices include heat responsive elements which exert forces when they are heated by the radiant energy from the sun and become limp when shaded. When the heat responsive element is heated by the solar energy within a certain range of the azimuth or altitude angle, the solar collector can be rotated to a position to face the position of the sun. The latter one U.S. Patent also discloses a device which is provided for turning a parabolic trough solar collector about an east-west horizontal axis and the alignment of the solar collector is accomplished by the heating of a long wire held in tension by a spring.
These ideas in prior patents, however, cannot always satisfy our requirement for tracking mechanisms of solar collectors for the reason that the tracking mechanisms of the former two patents can change their position to only two, three at maximum, positions of the movement of the sun with time. The latter one patent cannot track the sun after the sun has been covered with clouds for a certain time period, and from the same reason, tracking of the sun about the north-south axis cannot be realized. Furthermore, the application of this mechanism is limited to solar collectors with a parabolic trough reflector. These defects or disadvantages of the tracking mechanisms disclosed in the prior patents will be understood by those skilled in the art from the disclosures of these patents.
In addition, an improved self-tracking mechanism for a solar collector has been proposed by the same inventor of this application as U.S. Pat. No. 4,498,456, for eliminating the defects encountered with the prior art such as the three U.S. Patents referred to above. Although this self-tracking mechanism can track the movement of the sun with time, this mechanism can perform the tracking operation only intermittently.